The invention relates to a transparent wrapping for bulk goods which are first wrapped in a plastic film, then shrunk and, subsequently, wrapped in an additional plastic film and also shrunk. For this purpose films of a different composition are used for the individual wrapping and the overall wrapping.
Bulk goods, particularly boxes and cassettes, are in many cases wrapped in transparent film for a more appealing look as well as to provide a tight sealing. After the heat sealing of the film, the wrapping process can be followed by a short shrinkage process resulting in a very close-fitting wrapping which, simultaneously, presents the wrapped goods in a visually very appealing way. At the same time the goods are protected from dust, moisture and contact.
When the goods to be wrapped are small in size, they are usually compiled in batch packages; i.e the already wrapped individual parts are combined to form a larger batch package and then wrapped again. It is the object to select the wrapping such that the contents are visible through both wrappings; i.e. generally a transparent film is also selected for the overall wrapping; the internal wrapping as well as the external wrapping can partially be provided with an imprint. This way of wrapping also causes problems. If the same kind of film is used for both the surrounding wrapping and the individual wrapping, the sealing areas of the surrounding wrapping are bonded to the sealing areas of the individual areas; i.e. when the package is opened, the surrounding wrapping as well as the individual wrapping are destroyed. The same effect occurs when the batch package is subsequently passed through a shrinking oven so as to provide a very close-fitting, smooth wrapping.
In order to prevent a bonding of the internal wrapping to the surrounding wrapping, it is known to coat or spray separating agents onto the individual wrapping. Further, from DE-AS 22 35 748 it is known to incorporate dimethylpolysiloxane oil in the shrinkage film. Both methods have disadvantages insofar as the first one requires an additional operational step and additional material; the second one prevents a bonding of the films when the temperatures are increased for a short period of time as occurs during shrinking. However, the bonding of the sealing joints cannot be avoided such that when the external wrapping is heat sealed, the internal and the external film are still sealed together.
The German publication DE-GM 19 82 961 discloses a batch package wherein the individual packages are made of a compound film which has a 50.mu. thick ethylene layer and a 20.mu. thick polyamide layer and the external wrapping is made of 150.mu. thick polyethylene film. Wrappings of this kind do not exhibit the desired transparency nor can they be stretched tightly by means of shrinking after the heat sealing is completed since the polyamide together with the polyethylene does not provide a sufficiently strong sealing connection.
Hence, it was common to use as a film for the internal wrapping a PVC-film, to stack the goods wrapped therein and provide a wrapping using a polyolefin film and not shrink the latter. However, this adversely affects the visual impression as well as the stability since the goods slide on each other and are thus displaced within the stack.